Anyway, I abandoned Quick Sync months ago. While it is ridiculously fast, the resultant files were just not acceptable no matter what I tried. I got it "fairly good' after awhile, and if my point was to share mid-quality files on the net or watch them on a 3" screen that'd be fine... but I was looking to archive my DVD collection and it was nowhere near good enough. Instead I used my graphics cards' hardware and handbrake. It takes 2-3 times as long but the quality is SO much better its not funny.

- Steven

It looks like you found out the same way as me how poor Quicksync is; funny how very few of the articles at the time mentioned it. It is very limited, won't ever support 2-pass encoding and probably only equivalent to x264 Ultra fast setting - which is not for anything of quality.
Handbrake and Cuda are good for x264 but don't use them for Xvid encoding.